1 . Field of the Invention
The present invention relates generally to an image forming apparatus, and in particular relates to an image forming apparatus in which a printing part is drawn toward the front side of the apparatus so that the printing part can be easily replaced.
2 . Discussion of the Background
An image forming apparatus using an ink jet process is relatively simple in configuration when compared with an image forming apparatus performing optical writing by scanning a laser beam. Generally each component of a printing part of the apparatus is mounted to a frame of the apparatus. When repair is necessary to the printing part, the apparatus itself is replaced or each component of the printing part in need of repair is replaced.
Japanese Patent Application Publication No. 2002-506758 describes a hard copy apparatus as an image forming apparatus in which each component of a printing part is replaceable. The hard copy apparatus is configured in such a way that it includes: a writing engine device as the printing part, an ink jet printing module which transfers ink to a print medium, a service module which maintains ink jet printing functional integrity of the writing engine device, at least one ink, at least one ink containing module which contains a predetermined quantity of said ink, a delivery module which delivers said ink from said ink containing module to said ink jet printing module, and an electrical module which connects power and control to said writing engine device all housed in a housing module in respective operational configurations as selectively replaceable units within the hard copy apparatus.
When repair is necessary to a printing part in an image forming apparatus using an ink jet process (ink jet printing apparatus), replacing each component of the printing part in need of repair is inefficient in working efficiency because liquid ink is used and thereby careful attention is needed. That is, in the ink jet printing apparatus, because ink needs to be supplied to an ink jet printing module including printing heads, a mechanism to supply the ink to the ink jet printing module, e.g., ink supplying tubes or ink supplying conduits, are connected with the ink jet printing module. When replacing the inkjet printing module, for example, after disconnecting such ink supplying tubes or conduits from the ink jet printing module, the ink jet printing module is detached from the apparatus, and when attaching the ink jet printing module to the apparatus, the ink supplying tubes or conduits must be attached to the ink jet printing module again. Thus, the work of replacing the ink jet printing module takes a relatively long time because it involves detachment of ink supplying tubes or conduits.
Further, when replacing the ink jet printing module, because of a possibility of ink leakage, ink in the ink jet printing head (in a sub-tank) must be removed, and in performing the replacing work, attention must be paid to a difference in ink level between the sub-tank and a main tank. If ink leaks, the inside of the apparatus might be soiled, or the floor of the customer's premises where the apparatus is placed might be soiled. In order to avoid such ink leakage, the work must be performed very carefully, which further lengthens the time of replacing the ink jet printing module. If the inside of the apparatus or the floor of the customer's premises is soiled, it takes time and trouble to clean the inside of the apparatus or the floor; thereby the working efficiency is further decreased.
In relation to the above-described problem, Japanese Patent Publication No. 3167486 describes an ink jet printing apparatus as an image forming apparatus in which a printing part is replaceable as an integrated unit. The ink jet printing apparatus includes an ink jet printing head opposing and moving relative to a printing sheet, a fixed ink storage device as a supply source supplying ink to the ink jet printing head, an ink supplying tube supplying the ink in the fixed ink storage device to the ink jet printing head, and a connecting cable connecting a drive circuit and an electrode of the ink jet printing head with each other. The ink jet printing head and its driving device, the fixed ink storage device, the ink supplying tube, and the connecting cable and its connecting terminal are mounted to a support member to be configured as an integrated replaceable unit, and the support member is configured to be detachably attached to the main body of the apparatus. Specifically, the replaceable unit including the ink jet printing head, the fixed ink storage device, etc. is attached to an upper surface of the main body of the apparatus from above through the intermediary of an attaching axis, and is fixed by a hook at a side surface of the main body. Accordingly, in this case, the ink jet printing head, the ink supplying mechanism including the fixed ink storage device, and the connecting cable and its terminal can be replaced as an integrated unit. However, the replacing work to the unit must be performed from above, so that an upper space of the main body must be open. Further, a sheet feeding and conveying mechanism including a platen roller and its driving system and a drive source of the ink jet printing head are provided at the side of the main body of the apparatus, separately from the replaceable unit. Thus, the ink jet printing head is structurally independent from the drive source of the ink jet printing head and the sheet feeding and conveying mechanism. When the printing part including the ink jet printing head is replaced, it is hard to keep a distance between the ink jet printing head and the sheet feeding and conveying mechanism and to keep their relative positions the same as before replacing the printing part. Thus, there is a limit in printing accuracy that can be obtained after replacement of the printing part.
Further, when detaching the printing part from the main body of the apparatus, as described also in JP publication NO. 3167486, electrical systems connecting the printing part and the main body must be also detached. In an ink jet printing apparatus, because an ink jet printing head includes many nozzles and these nozzles must be controlled, the number of connecting pins for connecting the printing part and a control board of the main body reaches 100 to 200. When the number of connecting pins is large, a drawer-type connector is ideal. However, a relatively large power is needed in pulling and inserting hundreds of pins, so that under present circumstances, a connector having hundreds of pins is not available, and generally, plural connectors are used.
In an ink jet printing apparatus, a control part of the main body of the apparatus is often arranged at the rear side of the main body of the apparatus because of a need to perform clearance of a jammed sheet and replacement of an ink cartridge from the front side of the apparatus. Therefore, when the control part of the main body of the apparatus is arranged at the rear side of the main body and connectors for connecting electrical systems connecting a printing part of the apparatus and the control part of the main body are arranged at the front side of the apparatus, connecting cables must be wired from the rear side to the front side of the apparatus. This results in the connecting cables connecting the printing part and the control part of the main body being made longer, which increases a possibility of picking-up noise, and thereby a problem may be caused in printing control. When the connectors are arranged at the rear side of the apparatus, the apparatus itself must be first drawn to this side to disconnect the connectors, which is inconvenient.